The material to be sieved or milled consists of coarser and finer particles which are entrained in an air stream, and which form the product stream that is introduced into a housing of an air classifier of the jet mill. The product stream reaches, in the radial direction, a sieve wheel of the air classifier. In the sieve wheel, the coarser particles are separated from the air stream, and the air stream with the fine particles axially leave the sieve wheel through an outflow pipe. The air stream with the fine particles to be removed by filtration or to be produced can then be fed to a filter, in which a fluid, for example, air, and fine particles are separated from each other.
From DE 198 24 062 A1, a jet mill is known into whose milling chamber moreover at least one energy-rich grinding stream made of hot steam with high flow energy is introduced, where the milling chamber has, besides the inlet device for the at least one milling jet, an inlet for the mill material and an outlet for the product, and where, in the area where the mill material and at least one milling jet made of hot steam and mill material have at least approximately the same temperature in the area where they converge.
Furthermore, a corresponding air classifier is known particularly for a jet mill, for example, from EP 0 472 930 B1. This air classifier and its operating procedure are quite satisfactory in principle.